Volcanic Activity Summary: Based on the low level of seismic activity and lack of any obvious outward signs of progressing unrest, AVO is lowering the Aviation Color Code and Volcano Alert Level at Redoubt Volcano to GREEN/NORMAL.

The swarm of small, shallow earthquakes that began Sunday, December 27 has ceased and the degree of seismic activity beneath the volcano has returned to background levels. Aerial observations of the new lava dome on December 31 indicated no obvious changes at the surface and no sign of instability. Thermal images also obtained on December 31 indicate that parts of the dome are still hot, although most of the dome surface remains cold and snow covered. Magmatic gas emission from the dome area on December 31 was slightly elevated compared to the last measurement in early November, but not enough to warrant great concern.

It is likely that existing magma within the volcano's shallow plumbing system was temporarily remobilized, causing the increase in seismicity, but this process appears to have ended. It is possible for activity to resume at any time and if it does, we expect to observe a distinct increase in seismicity as well as other outward signs of unrest such as increased melting and steaming in the vicinity of the lava dome or rock fall activity on the slopes of the dome.

Remarks: AVO will continue to monitor conditions at Redoubt, but while we have no volcanoes at elevated color codes or alert levels, we will cease our usual daily reporting of activity and instead transmit a weekly summary only.

Heavily ice-mantled Redoubt volcano is located on the western side of Cook Inlet, 170 km (106 mi) southwest of Anchorage and 82 km (51 mi) west of Kenai, within Lake Clark National Park. Redoubt is a stratovolcano which rises to 10,197 feet above sea level. Recent eruptions occurred in 1902, 1966-68, 1989-90, and 2009. The 1989-90 and 2009 eruptions produced mudflows, or lahars, that traveled down the Drift River and partially flooded the Drift River Oil Terminal facility. The ash plumes produced by the 1989-90 and 2009 eruptions significantly disrupted air traffic and resulted in minor or trace amounts of ash in the city of Anchorage and other communities in south-central and interior Alaska.

Next Notice: A new VAN will be issued if conditions change significantly or alert levels are modified. While a VAN is in effect, regularly scheduled updates are posted athttp://www.avo.alaska.edu

The Alaska Volcano Observatory is a cooperative program of the U.S. Geological Survey, the University of Alaska Fairbanks Geophysical Institute, and the Alaska Division of Geological and Geophysical Surveys.

(1) VOLCANO OBSERVATORY NOTICE FOR AVIATION (VONA)

(2) Issued:

(20100106/0032Z)

(3) Volcano:

Redoubt (CAVW# 1103-03-)

(4) Current Color Code:

GREEN

(5) Previous Color Code:

yellow

(6) Source:

Alaska Volcano Observatory

(7) Notice Number:

2010/A1

(8) Volcano Location:

N 60 deg 29 min W 152 deg 44 min

(9) Area:

Cook Inlet-South Central Alaska

(10) Summit Elevation:

10197 ft (3108 m)

(11) Volcanic Activity Summary:

Based on the low level of seismic activity and lack of any obvious outward signs of progressing unrest, AVO is lowering the Aviation Color Code and Volcano Alert Level at Redoubt Volcano to GREEN/NORMAL.

The swarm of small, shallow earthquakes that began Sunday, December 27 has ceased and the degree of seismic activity beneath the volcano has returned to background levels. Aerial observations of the new lava dome on December 31 indicated no obvious changes at the surface and no sign of instability. Thermal images also obtained on December 31 indicate that parts of the dome are still hot, although most of the dome surface remains cold and snow covered. Magmatic gas emission from the dome area on December 31 was slightly elevated compared to the last measurement in early November, but not enough to warrant great concern.

It is likely that existing magma within the volcano's shallow plumbing system was temporarily remobilized, causing the increase in seismicity, but this process appears to have ended. It is possible for activity to resume at any time and if it does, we expect to observe a distinct increase in seismicity as well as other outward signs of unrest such as increased melting and steaming in the vicinity of the lava dome or rock fall activity on the slopes of the dome.

(12) Volcanic cloud height:

Unknown

(13) Other volcanic cloud information:

Unknown

(14) Remarks:

AVO will continue to monitor conditions at Redoubt, but while we have no volcanoes at elevated color codes or alert levels, we will cease our usual daily reporting of activity and instead transmit a weekly summary only.

Heavily ice-mantled Redoubt volcano is located on the western side of Cook Inlet, 170 km (106 mi) southwest of Anchorage and 82 km (51 mi) west of Kenai, within Lake Clark National Park. Redoubt is a stratovolcano which rises to 10,197 feet above sea level. Recent eruptions occurred in 1902, 1966-68, 1989-90, and 2009. The 1989-90 and 2009 eruptions produced mudflows, or lahars, that traveled down the Drift River and partially flooded the Drift River Oil Terminal facility. The ash plumes produced by the 1989-90 and 2009 eruptions significantly disrupted air traffic and resulted in minor or trace amounts of ash in the city of Anchorage and other communities in south-central and interior Alaska.

A new VONA will be issued if conditions change significantly or alert levels are modified. While a VONA is in effect, regularly scheduled updates are posted athttp://www.avo.alaska.edu

VOLCANO ALERT LEVELS

NORMALVolcano is in typical background, noneruptive state or, after a change from a higher level, volcanic activity has ceased and volcano has returned to noneruptive background state.

ADVISORYVolcano is exhibiting signs of elevated unrest above known background level or, after a change from a higher level, volcanic activity has decreased significantly but continues to be closely monitored for possible renewed increase.

WATCHVolcano is exhibiting heightened or escalating unrest with increased potential of eruption, timeframe uncertain, OR eruption is underway but poses limited hazards.

WARNINGHazardous eruption is imminent, underway, or suspected.

AVIATION COLOR CODES

GREENVolcano is in typical background, noneruptive state or, after a change from a higher level, volcanic activity has ceased and volcano has returned to noneruptive background state.

YELLOWVolcano is exhibiting signs of elevated unrest above known background level or, after a change from a higher level, volcanic activity has decreased significantly but continues to be closely monitored for possible renewed increase.

ORANGEVolcano is exhibiting heightened or escalating unrest with increased potential of eruption, timeframe uncertain, OR eruption is underway with no or minor volcanic-ash emissions [ash-plume height specified, if possible].

REDEruption is imminent with significant emission of volcanic ash into the atmosphere likely OR eruption is underway or suspected with significant emission of volcanic ash into the atmosphere [ash-plume height specified, if possible].